Page 23 - June SRG

Slippery rock Gazette
White Granite, White Quartzite, and White Marble
example, if a stone does not get buried too deeply when it forms, tiny spaces can remain between mineral grains. Another possible cause of porosity is underground fracturing along fault lines where rocks grind up against each other. Sometimes groundwater dissolves away pieces of the stone. On the other hand, groundwater can also do the opposite – it can add bits of minerals that will fill in pore spaces.
So we just have to live with the fact that sometimes granite, marble, and quartzite are slightly porous, and sometimes they are not. That also means that poros- ity cannot be a guide to helping us identify a stone. We can’t say that a stone is porous therefore it’s marble, for example. Because plenty of marbles are dense and impermeable. The same is true for granite and quartzite, too.
The porosity of quartzite can be especially confusing, and you can learn more in my article Deep Dive Into the Properties of Quartzite. (See the March 2020 SRG archive, www.slipperyrock gazette.net )
So while rules of thumb some- times fail us, what we can do is test slabs to learn about their po- rosity – which is actually ideal, because you’ll get specific details on the slabs of interest.
Next month’s article will share instructions and photos showing how to test your slab’s hardness, acid sensitivity, and porosity. Nothing can beat the hands-on in- formation you’ll get from doing a little “sciencing” on various slabs, and it’s pretty fun, too.
So don’t let the array of white stones get the better of you. By learning a bit more about why dif- ferent stones have their particular aesthetics and properties, you’ll be able to enjoy them all the more.
Karin Kirk is a geologist and science educator with over 20 years of experience and brings a different perspective to the stone industry. Karin is a regular con- tributor to usenaturalstone.com and the Slippery Rock Gazette. Contact her at karinkirk@gmail. com .
The pattern of swooping cross-bedding is unique to quartzite and sandstone. Cross beds can be caused by wind (sand dunes) or water (ripple marks). In this photo of Infinity White quartzite, small stream channels were flowing toward the viewer, and laying down layers (beds) of fine-grained deposits.
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Granite, marble and quartzite can be porous, or not.
Some types of stone have small pore spaces within the stone, and a porous stone can absorb liq- uids and become stained. There are several geologic processes that affect a stone’s porosity. For
June 2020|23 Gator Daze
Around this time of year, Floridians don’t just have to worry about aggressive tour- ist drivers on the road — they should be on the lookout for aggressive alligators, too, ac- cording to officials who had to remove a 9-foot (2.8-meter) gator from a county road.
The Manatee County Sheriff’s Office warned motorists that it’s that time of year when alliga- tors, um, fall in love but might not always be so affectionate.
“It’s gator mating season. This means they could be more mobile and aggressive than usual,” the sheriff’s office wrote in a Facebook post.
A male gator measuring 9 feet, 2 inches (2.8 meters) had to be removed from a roadway after it was spotted “being ag- gressive with traffic.” Sheriff’s deputies captured the reptile and relocated him to an alliga- tor farm.
Wildlife officials say mat- ing season in Florida begins in early April and could continue into June. You’ve been warned.
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